Environment: Uncovering unknown by-products of coal burning

Nature Communications

August 9, 2017

A new potentially toxic mineral compound has been found in large quantities in coal ash samples analysed in a study published in Nature Communications this week. These findings provide a new environmental marker for monitoring emissions from coal burning. However, it should be noted that the potential toxic effects of this compound were tested in zebrafish and have not yet been assessed for humans.

Coal burning is known to have potentially severe environmental and human health impacts. Particulate matter generated from coal burning can contribute to air pollution; particles with a diameter smaller than 2.5 μm have been estimated to cause 3.3 million premature deaths per year worldwide.

Michael Hochella and colleagues analyse coal ash samples taken from 12 coal-burning power plants in the United States and China. They discover that nanoscale titania suboxide particles - a previously unknown by-product of coal-burning - are present in large quantities of all samples. These particles, so-called Magneli phases, are generated from the burning of titanium oxide TiO2 minerals naturally present in coal. The authors suggest that these mineral compounds could be used as an environmental marker globally to assess the impact of coal burning.

The team also tested the toxicity using zebrafish and found that Magneli phases may have detrimental effects on zebrafish embryos under certain environmental conditions. However, they stress that the toxicity will be need to be tested further in relation to effects in human tissues.